St Johnstone manager Tommy Wright revealed match winner Danny Swanson almost did not play in his side's 1-0 win over Celtic.
Swanson hit a 25-yard strike in the second half to move Saints into the top six and end Celtic's 11-game unbeaten domestic run.
"It was worthy to win any game," Wright told BBC Scotland. "It's a tremendous strike and he's got that in his locker.
"He phoned this morning to say he wasn't feeling great."
Wright thought that Swanson might not be able to start the game and the on-loan Coventry City midfielder was substituted after his goal.
"I thought on a big pitch if we were going to keep the ball he would help us and I was pleased with Danny's all-round performance," said the manager.
"The team was magnificent and you have to be to come here and get a result.
"We asked them to be brave in possession. We didn't have to be backs-to-the-wall defending for too long in the game and I thought we controlled and passed the ball really well, which gave us a platform to go on and win the game.
"If you're brave enough, you can play here.
"I think most people thought we wouldn't get any points tonight, but that squad has went and won in Rosenborg, so we're capable of results like that.
"I'm really delighted with the performance. They've been really good in recent weeks, but to come here and play on this stage and play against the team that's flying shows a lot of character and a lot of belief in each other."
Celtic manager Ronny Deila said his men were tired after a run of two games a week stretching back to three weeks, which included Europa League ties with Inter Milan and 4-0 victories over Aberdeen and Hamilton Academical.
However, he felt his side's performance was not good enough and urged them to make up for it with victory over Dundee United in the Scottish Cup at the weekend.
"We have been good for a long time now and today was a big setback," he said.
"It's disappointing, but it's happened now. We just have to bounce back on Sunday.
"You have to start by winning challenges, and fight, and be a unit in the defence. And then in the attacking play get much wider.
"We started the game well and got some chances, but we didn't create anything in the wide areas and, when they are so crowded in central, we get problems.
"Every team loses, so that's something we have to live with now. We have to learn from this and it's four days before we can make it good again.
"We have won a lot of games and today there was some tired players out there, but we should be better as a unit."